Price and time saved difference between HS2 at 225mph and 185mph

[Justin Smith]

How much cheaper would HS2 have been to build had it been designed for - say - 185mph (or even 150mph), and how much difference in the end to end journey time would it have made ?

 

[JamesT]

How much cheaper would HS2 have been to build had it been designed for - say - 185mph (or even 150mph), and how much difference in the end to end journey time would it have made ?

The official estimate was that a 125mph railway would have been 9% cheaper., therefore an intermediate speed would have less of a saving.
On one of the other recent HS2 threads someone has produced a table comparing the times with 300kph running.

 

[Justin Smith]

The official estimate was that a 125mph railway would have been 9% cheaper., therefore an intermediate speed would have less of a saving.
On one of the other recent HS2 threads someone has produced a table comparing the times with 300kph running.

125mph may have been too slow, how about 150mph or 175mph ?
I never could understand why they designed HS2 for 225mph in this relatively small country of ours....

 

[35B]

Without comment on what the "right" speed would be, cost of construction is only one part of the decision. The other is the benefit of building that railway, where the benefit:cost ratio equations put a value on saving time.

 

[Djgr]

125mph may have been too slow, how about 150mph or 175mph ?
I never could understand why they designed HS2 for 225mph in this relatively small country of ours....

Well if it is actually only 9% more expensive for nearly twice the speed, sounds like a bargain

 

[JamesT]

125mph may have been too slow, how about 150mph or 175mph ?
I never could understand why they designed HS2 for 225mph in this relatively small country of ours....

125mph was chosen as the comparison because that's a standard UK mainline. Once you've decided you're building a high speed line, why wouldn't you build to the same standard everyone else has been building to?
You're saying it's a small country, but knocking half an hour off the London to Manchester or Glasgow times isn't to be sniffed at. Especially for the latter, getting to 4 hour journey time might be enough to swing some travellers to use the train instead of the plane.
Finally, as @TheHam has shown in many postings, going faster can save money. If you can get more round-trips per day out of your rolling stock, you don't need to buy as many to provide your service. (Or need as many crew etc.)

 

[Justin Smith]

125mph was chosen as the comparison because that's a standard UK mainline. Once you've decided you're building a high speed line, why wouldn't you build to the same standard everyone else has been building to?
You're saying it's a small country, but knocking half an hour off the London to Manchester or Glasgow times isn't to be sniffed at. Especially for the latter, getting to 4 hour journey time might be enough to swing some travellers to use the train instead of the plane.
Finally, as @TheHam has shown in many postings, going faster can save money. If you can get more round-trips per day out of your rolling stock, you don't need to buy as many to provide your service. (Or need as many crew etc.)

So why is 187mph, or 200mph later, OK for a huge country like France ?
And what would the time saved difference be at - say - 150mph over 225mph for London to Manchester ?
I thought one the main reasons for the construction of HS2 was to increase capacity anyway ? Even 125mph would help with that ! And if the latter trains could use normal tracks at each end I start to wonder how much time (overall) is actually saved by going for 225mph.....

 

[quantinghome]

As has been pointed out in the other thread, this is true but only to a point. Various obscure and complex engineering issues start to rear their heads once you push beyond speed of 300-320 km/h which will disproportionately impact costs.

Going from 200 km/h to 300 km/h for a new build intercity line is probably a no-brainer. But going much beyond that requires careful consideration of the costs and benefits - the key point wrt benefits being that these impressive sounding increases in speed don't actually knock that many minutes off the journey for an island the size of Britain where the longest high speed line will only ever be 400 miles.

 

[JamesT]

So why is 187mph, or 200mph later, OK for a huge country like France ?
And what would the time saved difference be at - say - 150mph over 225mph for London to Manchester ?
I thought one the main reasons for the construction of HS2 was to increase capacity anyway ? Even 125mph would help with that ! And if the latter trains could use normal tracks at each end I start to wonder how much time (overall) is actually saved by going for 225mph.....

Because they started earlier so are constrained by having lots of existing routes and rolling stock that are only capable of those slower speeds. The French are still building their new routes to the same speed specification as we're building HS2 to, and have ordered trains capable of 215mph running.
It's hard to say what times a 150mph line would get, not all of the new line is at full speed, so you can't just divide one by the other. Also, one of the reasons why people would suggest for a lower speed is that it makes it easier to go around obstacles, so you're looking at a longer route with that. The published figures are 2:08 for the current route at 125mph max, versus 1:40 with HS built in full. I would contend 150mph is going to be considerably nearer the existing time.

As has been pointed out in the other thread, this is true but only to a point. Various obscure and complex engineering issues start to rear their heads once you push beyond speed of 300-320 km/h which will disproportionately impact costs.

Going from 200 km/h to 300 km/h for a new build intercity line is probably a no-brainer. But going much beyond that requires careful consideration of the costs and benefits - the key point wrt benefits being that these impressive sounding increases in speed don't actually knock that many minutes off the journey for an island the size of Britain where the longest high speed line will only ever be 400 miles.

This has been stated, but where's the evidence? Is everyone else ignoring these complex engineering issues to build their lines to this speed? (Or in the case of the Chinese, even faster)

Are you suggesting the years of scrutiny in parliament before the HS2 acts were passed was not careful? The benefits were determined to outweigh the costs then.

 

[CW2]

During the early planning stages of HS2, senior staff discussed the operational design requirements with European colleagues in France, Spain, Germany and Italy. In every case, amongst the lessons learned was the statement "We wish we had designed our lines for higher speeds from the outset". This underpinned the design philosophy of HS2. You don't get (say) a 25% cost reduction by designing it to run 25% slower, so why not build it for a higher speed from the outset?

 

[Justin Smith]

This has been stated, but where's the evidence? Is everyone else ignoring these complex engineering issues to build their lines to this speed? (Or in the case of the Chinese, even faster)

They are countries with much more room, uninhabited land, than us ?

== Doublepost prevention - post automatically merged: 24 Mar 2026 ==

During the early planning stages of HS2, senior staff discussed the operational design requirements with European colleagues in France, Spain, Germany and Italy. In every case, amongst the lessons learned was the statement "We wish we had designed our lines for higher speeds from the outset". This underpinned the design philosophy of HS2. You don't get (say) a 25% cost reduction by designing it to run 25% slower, so why not build it for a higher speed from the outset?

Surely it's cost v benefit, and has been pointed out in a relatively small country like ours the benefit from 225mph running is not going to be as high. On the other hand in a densely populated country like ours the cost is going to be higher as well, much higher. We went on the AVE in Spain from Madrid to Cordoba, not many tunnels for environmental reasons (because of local populations) on that.....

 

[35B]

They are countries with much more room, uninhabited land, than us ?

And Japan?

Surely it's cost v benefit, and has been pointed out in a relatively small country like ours the benefit from 225mph running is not going to be as high. On the other hand in a densely populated country like ours the cost is going to be higher as well, much higher. We went on the AVE in Spain from Madrid to Cordoba, not many tunnels for environmental reasons (because of local populations) on that.....

You may want to consider the politics that went into giving those tunnels away to local protests.

The benefits case was enhanced by higher speed, because of the value associated with reducing travel time.

 

[Justin Smith]

You may want to consider the politics that went into giving those tunnels away to local protests.

Quite, but in Spain and France (and even much of Germany) their lower population density meant they didn't have to do that so much, and they could make the lines straighter more easily.
Population density (people per Km2)

England = 443 (it's even higher if one excludes north of York and Preston or west of Bristol where HS2 was never going to be built anyway)
Japan = 343
Germany = 242
France = 122
Spain = 97

 

[quantinghome]

This has been stated, but where's the evidence? Is everyone else ignoring these complex engineering issues to build their lines to this speed? (Or in the case of the Chinese, even faster)

Are you suggesting the years of scrutiny in parliament before the HS2 acts were passed was not careful? The benefits were determined to outweigh the costs then.

Read the other thread where I gave some examples yesterday.

I've yet to see any parliamentary scrutiny report (or any report for that matter) which sets out a detailed comparison of maximum speeds for a high speed line (e.g. comparing 300, 330 and 360 km/h) and the relative costs and benefits. Maybe it exists somewhere but not one in the public domain that I'm aware of. As far as I can see, the 360km/h with future capable 400km/h specification got baked in at the start with little technical scrutiny - using the argument that other countries were looking at higher speeds, so why not future-proof it? It was only much later in the design process that the engineering difficulties became apparent. Although it should have been an obvious risk to push the envelope, and there should have been a much more serious look at how little gain it gave in terms of journey time.

== Doublepost prevention - post automatically merged: 24 Mar 2026 ==

The benefits case was enhanced by higher speed, because of the value associated with reducing travel time.

Up to a point. Certainly there's a benefit to go to high speed from the current maximum speed on conventional lines.

But this thread is about the difference between a 'conventional high speed' of ~300km/h vs a 'very high speed' of ~360km/h.

This table shows the journey time saving for a new build line with maximum speeds of 200, 300 and 360 km/h - assuming no intermediate stops and no constraints on speed other than acceleration/deceleration.

Journey time saving in minutes	London - Scotland (640km)	London - Manchester (300km)	London - Birmingham (190km)
200 > 300 km/h	60	26	15
300 > 360 km/h	19	8	4

The vast majority of savings are made from getting up to 300 km/h, with marginal gains beyond that.

 

[Peter Mugridge]

Well if it is actually only 9% more expensive for nearly twice the speed, sounds like a bargain

To be pedantic, if 125 mph is 9% cheaper than 225 mph, then 225 mph is actually 9.89% more expensive than 125 mph, but your point is excellent - it's an absolute bargain to just build ity for the higher speed and certainly future proofs it.

I wonder if that 9% cheaper statement takes into account the need for additional rolling stock and crews if it's running slower or if it's just the construction costs part of it? If it's just the construction costs then the actual price differential will be even smaller.

 

[Justin Smith]

This table shows the journey time saving for a new build line with maximum speeds of 200, 300 and 360 km/h - assuming no intermediate stops and no constraints on speed other than acceleration/deceleration.

Journey time saving in minutes	London - Scotland (640km)	London - Manchester (300km)	London - Birmingham (190km)
200 > 300 km/h	60	26	15
300 > 360 km/h	19	8	4

The vast majority of savings are made from getting up to 300 km/h, with marginal gains beyond that.

But how many of the journeys would be non stop ? And if the answer is nearly all then how sensible is that ?

 

[takno]

Surely it's cost v benefit, and has been pointed out in a relatively small country like ours the benefit from 225mph running is not going to be as high.

France is twice the area of the UK, but it's relatively square while mainland UK is long and thin. The distances between major cities in France aren't necessarily much greater than the distances in the UK.

In fact the UK is almost uniquely well-shaped to maximise benefit from a single very high speed spine running up the country. That's probably why they chose to build one.

 

[Sorcerer]

At a certain stage it does start to become less economical to run trains at a certain speed. Outside of Chinese examples where the distance might justify the extra energy consumption for lower time savings, 360-400 service speed won't be practical. But actual alignment and engineering would theoretically still permit it for simple futureproofing even if that never ends up happening.

This kind of engineering is perfectly normal on railways. TVM430, as the name suggests, can permit up to 430km/h (270mph) but this will obviously never happen in the foreseeable future. In HS2's case having it aligned for 360 is very much reasonable even if the trains in service only end up running at around 300-330 which is the sweet spot for current high-speed rail operation.

 

[quantinghome]

But how many of the journeys would be non stop ? And if the answer is nearly all then how sensible is that ?

Not sure what point you're trying to make. The table is a theoretical exercise looking at the relative gains of increasing the linespeed.

Are you asking what the relative gains would be if there were intermediate stops? Or are you questioning the purpose of having non-stop services on high speed lines?

 

[Justin Smith]

France is twice the area of the UK, but it's relatively square while mainland UK is long and thin. The distances between major cities in France aren't necessarily much greater than the distances in the UK.

In fact the UK is almost uniquely well-shaped to maximise benefit from a single very high speed spine running up the country. That's probably why they chose to build one.

In many ways I agree with you, though the distance from EB to London is 332m (as the crow flies) whereas from Lille to Marseille it's 500m.

 

[takno]

In many ways I agree with you, though the distance from EB to London is 332m (as the crow flies) whereas from Lille to Marseille it's 500m.

Personally I'd build along the Penzance-Aberdeen axis, but people do seem to make a fuss about London.

 

[Sorcerer]

Personally I'd build along the Penzance-Aberdeen axis, but people do seem to make a fuss about London.

Why wouldn't you? It's the most populated urban area of the UK with a comparable population of Scotland and Wales combined as well as the capital and focal point of the UK rail network. It's easily the most natural location for a new high-speed rail line. Considerably more so than Aberdeen and Penzance.

 

[Krokodil]

125mph may have been too slow, how about 150mph or 175mph ?

If a 125mph alignment would be only 9% cheaper than 225mph, you can be assured that a 186mph alignment (as for HS1) would save almost nothing.

I never could understand why they designed HS2 for 225mph in this relatively small country of ours....

Japan is currently building the Chūō Shinkansen. It will run at 314mph, despite the initial phase being shorter than London to Manchester and the full extent being roughly equivalent to London to Carlisle in distance - in the UK you'd be continuing to Edinburgh.

So why is 187mph, or 200mph later, OK for a huge country like France ?

186mph was the technology available at the time and the French have since realised that constraining themselves on that basis was a mistake. LGV Est was built to the same alignment standards as HS2.

In many ways I agree with you, though the distance from EB to London is 332m (as the crow flies) whereas from Lille to Marseille it's 500m.

A lot more people go from Edinburgh to London than go from Lille to Marseille.

 

[osmarks]

Personally I'd build along the Penzance-Aberdeen axis, but people do seem to make a fuss about London.

HS2 east would have served the middle of that. But it is much less busy overall than the ECML/WCML, though some of that must be down to the poor service.

 

[WTT Gremlin]

The Chūō Shinkansen for similar reasons with a different cause is also significantly above politically expedient cost and time estimates.

The original service TGV on LGV Sud-Est was at 270km/h though the stock was capable of considerably more. Also, interestingly the development line that led to the first squadron service TGV started with a gas turbine powered experimental prototype which evolved into 25kV AC powered multiple unit (in operation at least) due to the oil crisis.

 

[Krokodil]

HS2 east would have served the middle of that. But it is much less busy overall than the ECML/WCML, though some of that must be down to the poor service.

Indeed, HS2 East would have been revolutionary for Crosscountry. It would have knocked over an hour from the current timings between Birmingham and Leeds, just under that to York and Newcastle. An hourly Voyager (often a five though double sets are becoming more common) plus the odd extra would be replaced by three 200m units (one to York/Newcastle, two to Leeds). So 1,500 passengers leaving Birmingham per hour, against a current capacity averaging 400ish. With all of this capacity (plus the freed up paths that can be broken up into regional express trains serving the other stops), fares can be dropped to sensible levels on the route and rail travel becomes much more attractive for so many more people.

 

[Bald Rick]

We have done this several times before on previous threads.

Had it been, say, 270 or 300km/h instead of 360, the saving would have been a couple of %. The alignment would have been the same. The difference in cost would have been in what sits beneath the rails, but even then, it’s minimal difference.

 

[NCT]

We have done this several times before on previous threads.

Had it been, say, 270 or 300km/h instead of 360, the saving would have been a couple of %. The alignment would have been the same. The difference in cost would have been in what sits beneath the rails, but even then, it’s minimal difference.

To the best of your understanding, is there much difference in things like piling depth requirement between 300 and 360km/h? Or is simply HS2 Ltd over conservative tolerance specification regardless of the speed?

 

[Bald Rick]

To the best of your understanding, is there much difference in things like piling depth requirement between 300 and 360km/h? Or is simply HS2 Ltd over conservative tolerance specification regardless of the speed?

I don’t know I’m afraid.

What I do know is that the 17tph service provision and 360kph top speed meant ballasted track couldn’t cope, hence the slab. A lower top speed and lower service provision would have avoided this. Although slab has better whole life costs.

 

[Transilien]

To be pedantic, if 125 mph is 9% cheaper than 225 mph, then 225 mph is actually 9.89% more expensive than 125 mph, but your point is excellent - it's an absolute bargain to just build ity for the higher speed and certainly future proofs it.

Future proofs it for what? I remember reading that SNCF doesn’t run trains over 320km/h because of power draw issues. There doesn’t seem to be any obvious reason why trains should go above 320-330, perhaps this is the realistic maximum that traditional trains can reach in service.